1. Field of the Invention
The invention relates to a vertical transistor, and more particularly to a vertical transistor capable of generating an alternating current output.
2. Description of the Related Art
FIG. 1 illustrates a conventional vertical metal oxidation semiconductor field effect transistor (MOSFET) 1 that includes a substrate 11, a gate oxidation layer 12, and a gate layer 13 formed on the gate oxidation layer 12. The substrate 11 has a drain layer 111, and a protrusion 112 projecting from the drain layer 111. The protrusion 112 has a top surface 113, opposite first and second side surfaces 114, 115, a first source section 116 formed between the top surface 113 and the first side surface 114, and a second source section 117 formed between the top surface 113 and the second side surface 115. The gate oxidation layer 12 is formed on the first and second side surfaces 114, 115 of the protrusion 112, and on a part of the drain layer 111.
In operation, when a gate voltage is applied to the gate layer 13, a current channel 14 is formed in the protrusion 112 such that currents from the first and second source sections 116, 117 flow to the drain layer 111 through the current channel 14. In this case, the current channel 14 is controlled by an electric field applied to the gate layer 13 that is similar to a traditional MOSFET.
However, the conventional vertical MOSFET 1 generates a digital output. When the conventional vertical MOSFET 1 is required to output an AC analog output, an additional digital-to-analog converter is required, thereby increasing costs. Furthermore, the conventional vertical MOSFET 1 has limited applicability.